Our studies supported by grant R01 CA80054 have revealed the presence of membrane microdomains that control carbohydrate-dependent or carbohydrate-modulated cell adhesion coupled with signal transduction, termed "glycosynapses" (Glysyn). Structure and function of Glysyn are correlated closely with cell growth control and invasive/ metastatic properties of certain tumor cells: (i) Glysyn 1 consists of GM3, growth factor receptor, CD9 or CD81, Src family kinase, and its physiological inhibitor Csk. Its function in transformed cells is associated with loss of growth control (contact inhibition), (ii) Glysyn 3 consists of N-glycosylated integrin and tetraspanin (TSP) complexed with ganglioside (Gg) (particularly GM3), and inhibits integrin-dependent motility, as found originally in IdID cell model and later in various human cancer cell lines. Loss of malignancy, or "reversion" of oncogenic phenotype, may occur in these cells through increased Glysyn 3. This proposal has two major Specific Aims: 1. Elucidate the growth control mechanism in human normal epithelial cells vs. cancer cell lines, in analogy to previously-studied human lung fibroblast WI38 and oncogenically transformed VA13 cells. Studies are focused on: (a) Glysyn 1 composition as related to growth control, particularly Csk-dependent inhibition of Src kinase; (b) role of TSP CD9-CD81 in Glysyn 1 in facilitating contact inhibition of WI38 vs. its loss in VA13 cells; (c) role of GM3-to-FGFR interaction within the same Glysyn (cis interaction) or between interfacing Glysyn (trans interaction). 2. Elucidate the mechanisms by which Glysyn 3 controls tumor cell invasiveness. Studies are focused on: (a) characterization of components: TSPs, Gg, N-glycosylated integrins; (b) interactions among them; (c) correlation of such interaction with cell motility; (d) effects of Glysyn 3 components on integrin signaling; (e) reversion from malignant to non-malignant phenotype by modification of Glysyn 3 components.